HK1084408A1 - Two-component composition for producing polyurethane gel coats for epoxy-resin and vinyl-ester resin composite materials - Google Patents

Abstract

The invention relates to the use of a two-component composition comprising a polyol component and a polyisocyanate component, for producing polyurethane gel coats for epoxy-resin and vinyl-ester resin composite materials.

Description

The invention relates to the use of a two-component composition comprising a polyol component and a polyisocyanate component for the manufacture of polyurethane gel coatings for epoxy resin and vinyl ester resin composites.

The surfaces of composite materials (e.g. fibreglass composite materials and epoxy resin/vinyl resin) are often unsightly and not resistant to light and weather, so they need to be coated. The surface coating of epoxy resin/vinyl resin composite materials must be sanded and splattered, as the direct surface coating of the composite material leads to the formation of fibres.

US 4.267.299 A1 concerns solvent-free sprayable compounds for the manufacture of polyurethane and poly (urethane) coatings from isocyanate-terminated prepolymer or quasi-prepolymer, the products of these compounds and a process for the manufacture of such products.

A gelcoat is a resin system that can be applied to moulds in a composite manner to produce smooth component surfaces while also giving a good surface. In the in-mold process, the gelcoat resin system is first coated into a mould after mixing its reaction components within the processing time (potting time). The coating obtained after the geling is sufficiently mechanically stable to not be damaged by application of the artificial resin (e.g. epoxy resin) and, where appropriate, an inorganic or organic fibre or fabric (e.g. glass fibre or glass fibre pre-laminate). The same applies to injection processes and the application of wet laminates.

To ensure sufficient adhesion between (i) epoxy resin and/or vinyl ester resin (artificial resin) and (ii) gelcoat, the coating with artificial resin must be carried out within the lamination period of the gelcoat.

The following definitions shall apply to the description of the invention: The lamination time is the period starting from the time of free adhesion of the gelcoat film applied to the mould, during which the gelcoat film must be super-laminated to ensure an adhesion between the gelcoat and the laminate.The potting time is the period starting from the mixing of the two reaction compounds until the reaction mixture is gelled.Once the potting time is over, the reaction mixture is no longer processable.The free adhesion time is the period starting from the application of the homogeneous, mixed reaction mixture to the mould surface until the adhesion of the applied film is achieved.Meanwhile, the melting time is defined in E-DINDE V29 (EVDE1-2291-06-02): 9 to point 9.2.1 of the 1997 standard, measured in terms of reaction time.

For example, gelcoating systems are used in formulations based on radically hardening resins such as unsaturated polyester (UP), vinyl ester (VE) or acrylate-terminated oligomers. These resin systems are safe to use when used in combination with UP composites and show good adhesion to a variety of resins (composite adhesion) because due to oxygen-inhibited hardening reactions on the inner surface of the yellow coating, the curing of the border area occurs only after the application of the plastic resin. Vinyl ester based gelcoats lead to very poor plastic resistance and poor stability during the formation of new resins.

EP gel coats have a much better adhesion to EP composites than UP gel coats. EP gel coats also do not contain volatile monomers and are therefore less hygienic than the most styrene-containing UP gel coats. However, a disadvantage of EP gel coats is the low tolerance to inaccuracies in the mixing ratio. This can lead to a significantly reduced mechanical resistance, e.g. in the hardened form of gel coat.

In order to allow for early overlamination, EP gelcoats with high mesh density are often used. However, a high mesh density results in a high glass transition temperature Tg of the cured gelcoat (e.g. Tg = 70 °C for a commercially available SP-Systems pigmented EP gelcoat). The operating temperature of components such as rotor blades that are compensated with such gelcoats is usually far below the glass transition temperature of the gelcoat. Under these conditions of use, such gelcoats tend to crack at a high mechanical load.

In principle, therefore, gelcoats based on aliphatic polyurethanes should be preferred. However, when formulating PUR gelcoats, it should be borne in mind that conventional mixtures of polyol and polyisocyanate only gel until a very advanced reaction takes place. However, the reaction and thus the adhesion of the PU gelcoat is already very limited compared to the synthetic resin used for the composite material (i.e. the adhesion-free time is relatively long, while the lamination time is relatively short). The use of such a conventional product would be technically difficult to implement and, moreover, unreliable in terms of the gelcoat/synthetic adhesion.

Commercial aliphatic PUR gel coatings (from Relius Coatings or from Bergolin) generally have relatively low glass transition temperatures (< 40 °C). Therefore, they are less brittle than EP gel coatings. At curing temperatures well above the maximum Tg of the PUR gel coat (> 80 °C), these products often show surface defects in the form of gel deposits after deformation. This greatly limits the range of curing temperatures in which such a product can be used. Therefore, the use of PUR coatings at curing temperatures > 80 °C is only possible and/or requires a certain amount of post-processing to make the surface of the component more flexible.

The purpose of the invention is to provide components for a gelcoat resin system based on polyurethane for epoxy resin and/or vinyl ester resin composites which do not have the disadvantages mentioned. The product has a relatively long lamination time,with sufficient potting time and film-forming time,but relatively short gel and adhesive-free times,is easy to process (i.e. does not require additional equipment for hot application and/or spray application),provides a good adhesion between gelcoat and artificial resin (with long lamination times),provides a gelcoat with sufficient breaking resistance,and is not prone to hair cracking,provides a smooth component surface,free of patches even at hardening temperatures between 80°C and 130°C,products a sub-value and no release of hardness or environmental toxicity.

Although polyurethane gelcoats with a high mesh density would be particularly suitable for this purpose, a high mesh density requires the use of a high functional polyol, but the use of a high functional polyol involves a very short lamination time.

These tasks are accomplished according to the invention by using a two-component assembly which (a) a polyol component containing one or more polyols and one or more aromatic amines and having a hydroxyl group concentration of 0,5 to 10 mol of hydroxyl groups per kg of polyol component; and soluble in the manufacture of polyurethane gel coatings for resin composites, where the resin includes epoxy resin and/or vinyl ester resin and is not or not fully cured when in contact with the gel coat; polyol component A) is as defined in claim 1.

The invention is based, inter alia, on the finding that aromatic amines of a polyol component can be added to produce polyurethane gel coats and that the mixture produced from the polyol component and a polyisocyanate component of the invention has particularly good processing properties in the production of polyurethane gel coats and also produces a gel coat which is particularly mechanically resistant. The cured gel coats according to the invention preferably have a Shore D hardness of more than 65 (as determined by DIN EN ISO 868) and a refractive index of 23 °C preferably greater than 5 (as determined by DIN EN ISO 527) and give an excellent adhesion to Vinyl oxide and Vinyl oxide. All materials are suitable for use as a composite or as a commercial product.

The hardened composite material has an adhesive strength at the interface of resin-polyurethane gelcoat which is higher than the refractive strength of laminar resin, i.e. a cohesion break in the laminate or laminar resin is detected in the stamp fracture test. Polyurethane gelcoats manufactured according to the invention preferably have a refractive index (as measured in accordance with DIN EN ISO 527) of at least 3% at 23 °C, preferably greater than 4%, in particular greater than 5%.

The synthetic resin includes epoxy resin and/or vinyl ester resin, i.e. it is a synthetic resin based on epoxy resin and/or vinyl ester resin. In one preferred embodiment the synthetic resin is epoxy resin and/or vinyl ester resin and in one particularly preferred embodiment the synthetic resin is epoxy resin.

The applied resin is not or not completely cured when the bonding material is made, i.e. when it is brought into contact with the gelcoat. Preferably, the polyurethane gelcoat is not fully cured when it comes into contact with the resin (preferably when the resin is applied). This means that the conversion of isocyanate with hydroxyl groups to urethane groups is not yet fully completed in the gelcoat when it comes into contact with the resin (preferably when the resin is applied). In all embodiments, resins that include glass fibre tissue and/or glass fibre fibre fibres are preferred, whereby the pre-injected resin is a special pre-injected resin, in particular the pre-injected resin, which can be used as an injection/coating agent on glass.

In this case, the use of the two-component composition in an in-mold process is particularly preferable, where the polyurethane gel coating is partially but not yet fully cured and the artificial resin is not or not yet fully cured when brought into contact with the gel coating.

In particular, the invention relates to the use of a two-component composition in which the polyol component A) has a hydroxyl group concentration of 0,5 to 10 mol hydroxyl groups per kg of polyol component, A1) one or more low molecular weight polyols with a molecular weight of 150 to 600 g/mol and a hydroxyl group concentration of 4 to 20 mol of hydroxyl groups per kg of low molecular weight polyol,A2) one or more higher molecular weight polyols andA3) one or more aromatic amines.

1. polyol component

The hydroxyl group concentration of the polyol component is 0,5 to 10 mol per kg of polyol component. In preferred embodiments, the hydroxyl group concentration of the polyol component is 1 to 7, preferably 2,5 to 5, in particular, 2,0 to 4 mol of hydroxyl groups per kg of polyol component.

The polyol contained in the polyol component used in accordance with the invention may in principle be any polyol commonly used for the production of polyurethanes, e.g. polyester polyol, polyether polyol, acrylate polyol and/or polyol based on dimeric fatty acids.

The use of polyolefines of low molecular weight polyol and high molecular weight polyol is preferred, although high molecular weight polyol and low molecular weight polyol may be used separately provided that the hydroxyl group concentration of the polyol component is between 0,5 and 10 mol per kg of polyol component.

The preferred polyol component of the invention is characterised by the presence of at least one polyol with a comparatively low molecular weight and a comparatively high concentration of hydroxyl groups cOH. The low molecular polyol (or the two, three, four, etc. low molecular polyols, if any) supports the beneficial effect of the aromatic amine and leads to the formation of a very tight mesh network at the beginning of the reaction of the polyol component with a polyisocyanate component (after sufficient pot time and acceptable gel time) which ensures the desired mechanical stability of the gel coating of the gel. This strengthens the effect of the polyol component contained in the aromatic amine.

Low molecular weight polyols

Err1:Expecting ',' delimiter: line 1 column 67 (char 66)

Preferably the concentration of hydroxyl groups cOH is in the range of 4.5 to 15, preferably 5 to 12 and in particular in the range of 6 to 10 mol hydroxyl groups per kg of low molecular weight polyol.

In principle, all common straight-chain or branched-chain polyols, such as polyester polyols, polyether polyols such as polyether glycol, acrylate polyols and/or polyols based on dimeric fatty acids and mixtures thereof, are suitable as low molecular weight polyols, as exemplified by the low molecular weight polyols listed below: an acrylate-based polyol with a functionality of approximately 2,3 and a hydroxyl group content of 12,5 mol/kg,a polyether polyol with a functionality of 3 and a hydroxyl group content of approximately 16,5 mol/kg,a trimethyl propane and polycaprolactone transition product with a functionality of approximately 3 and a hydroxyl group content of approximately 10 mol/kg.

Preferably, the proportion of low molecular weight polyols (i.e. the sum of all low molecular weight polyols in the polyol component) is in the range of 2 to 70% by weight, preferably 5 to 60% by weight, in particular 10 to 50% by weight, such as 20 to 45% by weight, with a proportion of 35 to 45% by weight being particularly preferred, based on the total mass of polyol and aromatic amine (or the sum of components A1, A2 and A3) of the polyol component.

Other, of a width of

The higher molecular polyol contained in the preferred polyol component of the invention may in principle be any polyol commonly used for the production of polyurethanes, e.g. polyester polyol, polyether polyol, acrylate polyol and/or polyol based on dimeric fatty acids. The components A1 and A2 include all the polyols contained in the preferred polyol component of the invention, i.e. a polyol that is not a low molecular polyol as defined above is generally considered to be a higher molecular polyol for the purposes of this specification. The higher molecular polyols concerned have a molecular weight of more than 8000, preferably more than 600 to more than 6000 g/mol, in particular preferably more than 600 to more than 4000 g/mol.

For example, suitable higher molecular weight polyoles are described in the above mentioned DE-T-690 11 540. Preferred higher molecular weight polyoles are polyether polyoles (polyalkoxyl compounds) formed by polyaddition of propylene oxide and/or ethylene oxide on starter with low molecular weight OH groups and functionality from 2 to 8.

Other typical higher molecular weight polyols are polyether polyoles based on polyethylene oxide, polypropylene oxide or both, which have a functionality of 2-4 with preference given to higher molecular weight polyether polyoles with a hydroxyl group concentration in the range of 0,5 to 2,5 mol/kg higher molecular weight polyether polyoles, preferably 0,75 to 1,5 mol hydroxyl groups per kg. The high molecular weight polyol (or the two, three, four, etc. higher molecular weight polyols, as appropriate) strengthens the polyol component, which prolongs the lamination time of the aromatic amine. This is important to achieve a good adhesion to the resin of the composite.

High molecular weight polyols are particularly preferred: a polyether polyol based on polytetrahydrofuran with a functionality of about 2 and a hydroxyl group content of 1 mol/kg, a polyether polyol with a functionality of 3 and a hydroxyl group content of about 1 mol/kg, a transition product from neopentyl glycol and polycaprolactone with a functionality of about 3 and a hydroxyl group content of about 1 mol/kg.

Preferably, the proportion of higher molecular polyol (i.e. the sum of all higher molecular polyols) in the polyol component is in the range of 75 to 10%, preferably 65 to 10%, preferably 50 to 12%, and in particular 30 to 15%, based on the total mass of the polyol and aromatic amine (or the sum of the components A1, A2 and A3) of the polyol component.

Aromatic amine with low reactivity to isocyanates

The use of aromatic amines is recommended for the treatment of acute and chronic acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute acute

The preferred aromatic amines are characterised by the fact that, when dissolved in toluene (20% w/w amine in toluene) and mixed at 23 °C with an equimolar quantity of an oligomeric HDI isocyanate (hexamethylenediisocyanate) with an NCO of about 5,2 mol/kg and a viscosity in the range of 2750 to 4250 mPa, dissolved in toluene (80% w/w isocyanate in toluene), they give a gel time of more than 30 seconds, preferably more than 3 minutes, preferably more than 5 minutes and in particular more than 20 minutes.

The preferred aromatic amines of the invention are methylene bisanilins, particularly 4,4'-methylene bis ((2,6-dialkylaniline), preferably the non-mutagenic methylene bisanilins described in US-A-4 950 792. Other

Lonzacure M-DMA	H
Lonzacure M-MEA	H
Lonzacure M-DEA	H
Lonzacure M-MIPA	H
Lonzacure M-DIPA	H
Lonzacure M-CDEA	Cl

The particular preferred aromatic amine according to the invention is 4,4'-methylenbis ((3-chlor-2,6-diethylaniline), Lonzacure M-CDEA.

Preferably, the proportion of aromatic amine in the polyol component (i.e. the sum of all aromatic amines in the polyol component) is in the range of 0,1 to 20% by weight, preferably 0,3 to 10%, preferably 0,5 to 5%, and in particular 1 to 3%, based on the total mass of the polyol and aromatic amine (or the sum of the components A1, A2 and A3) of the polyol component.

Other, of circular cross-section

In principle, the polyol component can be made up of all catalysts known to be used in polyurethanes, preferably lead, bismuth and tin catalysts as described in DE-T-690 11 540, as well as the highly basic amine catalyst diazabicyclo ((2,2,2) octane-1,4 and zirconium compounds.

A catalyst according to the invention of particular preference for use in a polyol component is dibutyltin diurate (DBTL).

A polyol component used in accordance with the invention may contain up to 1% by weight, preferably 0,05 to 0,5% by weight, in particular about 0,3% by weight of catalyst, e.g. 0,3% by weight, based on the total mass of the polyol component.

Other, including:

Err1:Expecting ',' delimiter: line 1 column 197 (char 196)

In addition, the polyol component may contain ground glass fibres, such as ground glass fibres of a length of less than 500 μm. These glass fibres prevent further tearing of a possible crack.

The following is a list of the active substances:

Err1:Expecting ',' delimiter: line 1 column 418 (char 417)

The silica acids used as fillers in the polyisocyanate component are in particular silanised pyrogenic silica acids. The preferred content of the polyisocyanate component in silica (a thixotropic agent) ensures that the polyol component and the polyisocyanate component are well miscible due to the similar viscosities of the components and also prevents the mixing of the components on a vertical surface up to 1 mm wet layer thickness. The amount is preferably in the range of 0,1 to 5%, preferably 0,5 to 3%, in particular 1 to 2% by weight, based on the total mass of the polyisocyanate component.

Other, of circular cross-section

The catalysts that can be added to the polyol component may also be present in the polyisocyanate component, or in the polyisocyanate component instead of the polyol component, at the above concentrations, with the preference for zirconium compounds as catalysts in the polyisocyanate component.

Err1:Expecting ',' delimiter: line 1 column 71 (char 70)

In addition, either the polyol component or the polyisocyanate component, or both components, may additionally contain one or more additives selected from defoamers, dispersives and aerators.

Defoamers

may be present in amounts up to 2,0% by weight, preferably up to 1,0%, by weight, in relation to the total mass of the component in which they are used.

Other, including:

may be contained in amounts up to 2,0% by weight, preferably up to 1,0% by weight, depending on the total mass of the component in which they are used.

Other, of a kind used for the manufacture of paints or varnishes

may contain up to 2,0% by weight, preferably up to 1,0%, by weight, of the total mass of the component to which they are added.

When mixing the polyol component, the polyol (s) are typically presented with additives in a vacuum solvent. The fillers and pigments are then dispersed in the vacuum in the polyol (s). To mix the polyisocyanate component, the polyisocyanate is usually presented and mixed with the corresponding additives. The filler and thixotropic agent are then injected into the vacuum.

The relative amounts of polyol component and polyisocyanate component are chosen so that the hydroxyl groups and isocyanate groups react in the desired molar ratio respectively. The molar ratio of hydroxyl groups to isocyanate groups (OH: NCO) is usually in the range of 1:3 to 3:1; preferably 1:2 to 2:1; preferred 1:1.5 to 1.5:1.

The gelling of the mixture of the two components is done either at room temperature or, if accelerated gelling is desired, at an increased temperature. For example, gelling may be done at a temperature of 40 °C, 60 °C or even 80 °C. However, in the case of the particularly preferred mixture of the components of the two-component composition of the invention, an increase in temperature is not necessarily necessary to accelerate the gelling.

The synthetic resin preferably consists of one or more reinforcing materials, such as fabric, linings, nonwovens or preforms made by weaving or sewing, embedding or gluing of fabric, linings or nonwovens. These may consist of glass, carbon, aramid or polyester fibres or other plastic fibres.

When the formation of a mechanically stable gel is completed, epoxy and/or vinyl ester resin and, if desired, fiberglass fabric or fiberglass nonwovens are applied to the gel coating within the lamination time. Polyol components and bicomponents of the invention achieve lamination time available for eulamination in the range of about 20 minutes and 72 hours, typically about 48 hours.

Err1:Expecting ',' delimiter: line 1 column 192 (char 191)

The invention also relates to a process for the manufacture of synthetic resin composites with polyurethane gel coatings, which is (i) mixing a two-component composition which is (a) a polyol component containing one or more polyols and one or more aromatic amines and having a hydroxyl group concentration of 0,5 to 10 mol of hydroxyl groups per kg of polyol component; and and at least partial (and preferably partial) hardening of the mixture and (ii) includes the contact of the mixture with artificial resin, where the artificial resin includes epoxy and/or vinyl ester resin and is not or not fully hardened when in contact with the gel coating.

The invention also relates to a synthetic resin composite material with polyurethane gel coating, which is available by the above-mentioned process. A particularly preferred composite material is a windscreen, i.e. a rotor blade for wind turbines, or part thereof.

The two-component composition of the invention has the following advantages: It is a system of only two components and therefore easy to process. The potting time is only 5 to 15 minutes. The mixture of polyol component and polyisocyanate component is non-adhesive within 20 to 70 minutes, even at 0.5 mm layer thickness and room temperature. No heating is necessary. The lamination time at room temperature is more than 72 hours, which provides very good conditions for adhesion to resin laminates. The mixing of the two components is up to 1 mm wet layer thickness on a vertical drainage surface. The combination of the two components with the polyurethane isocyanate component, which is preferably placed with a mixer, gives a good predictability. The compounds used in the manufacture of the two components are hygienically handled and emission-free during processing. The two components give a transparent gelcoat, so they can be pigmented as desired. Transparent gelcoats also have the advantage that lamination defects such as bubbles in the resin, unsoaked areas of the reinforcing material, etc., can be detected immediately after manufacture. This prevents deformation. The mixed components can also be used as a spatula or coating that does not need to be applied in the in-mould process. The mixing of the components is self-conductive. Complete hardening of the mixture of the two components can be achieved within 2 hours at temperatures of 80 to 160 °C for two components in 30 minutes.

The gel coating according to the invention has the following advantageous properties: With a short gel and adhesive free time, a long lamination time. After deformation, smooth component surfaces without surface defects are obtained despite the relatively low glass transition temperature TG of about 50 °C. At operating temperature, a sufficiently high hardness (Shore hardness D > 65). No release of nonylphenol or other toxic or environmentally harmful substances during the curing reaction. High hydrolysis resistance. High chemical resistance. High abrasion resistance. Good abrasibility.

The invention is illustrated by the following examples.

Examples

Test methods used are described below:

Test method 1: Sufficiently low reactivity of preferred amine

To determine the boiling point, the aromatic amine dissolved in toluene (20% of the amine in toluene) is mixed at 23 °C with an equimolar quantity of an oligomeric HDI isocyanate with an NCO content of about 21,8% and a viscosity of the solvent-free isocyanate of 2750 to 4250 mPa dissolved in toluene (80% by weight of isocyanate in toluene, e.g. Desmodur N3300, Bayer AG).

Test method 2: Determination of TG of gelcoats

The glass transition temperature was determined by DSC measurements in accordance with DIN 51007 by heating a cured gelcoat sample at a rate of 10 K/min from -10 °C to 250 °C and determining the glass transition temperature from the heat flow by the sample according to the above standard.

Test method 3: Test of the liability between gelcoat and laminate

Err1:Expecting ',' delimiter: line 1 column 339 (char 338)

Example 1: Application of test method 1

The solubility time for aromatic amines was determined using test method 1. Other

Aromatisches Amin	Gelzeit
M-DEA	3575=5min57s
M-MIPA	221s=4min41s
M-CDEA	2635s=43min55s
M-DIPA	166s=2min46s

Example 2: Manufacture of polyol components

Polyol components have been formulated, the components of which are given in Table 3 below. Other

	Erfindungsgemäß	Nicht erfindungsgemäß
	Gewichtsteile	Gewichtsteile
Polyetherpolyol (OH-Gehalt ca. 7 mol/kg	38
Polyetherpolyol (OH-Gehalt ca. 1 mol/kg	20	60
4,4'-Methylen-bis(3-chlor-2,6-diethylanilin)	2
Füllstoffe (z.B. Talkum und Titandi-oxid)	30	30
Molekularsieb	10	10
Katalysator (z.B. DBTL)	0,2	0,2
Additiven	0,5	0,5

Example 3: Polyisocyanate components

Polyisocyanate components were formulated using the components listed in Table 4 below. Tabelle 4

	Gewichtsteile
Oligomeres 4,4'-Diphenylmethan-diisocyanat (MDI) (NCO-Gehalt ca. 7,5 mol/kg)	97,5
Pyrogene Kieselsäure	2
Additive	0,5

Example 4: Manufacture and testing of gelcoats

The following table 5 summarises the production and testing of gelcoats. The gelcoats were produced by mixing one polyol component and one polyisocyanate component, each, at a temperature of 20.5 to 24 °C, in such a ratio that a stoichiometric ratio of isocyanate groups to hydroxyl groups was obtained. The mixture was stirred for 1 minute. The mixture was applied in a 500 μm layer thickness to a steel form, which had been de-oiled with solvent and treated with a separating agent, e.g. Zx Watershield. Lamination adhesion, surface quality and glass transition temperature were then determined.

The fracture elongation (according to DIN EN ISO 527) was determined on non-laminated (free) gelcoats which had been cured at 50 °C for 7 hours.

	Stöchiometrische Mischung aus PA und HA	Stöchiometrische Mischung aus PB und HA	Handelsüblicher EP-Gelcoat I	Handelsüblicher EP-Gelcoat II
Haftung zum Laminat (Testmethode 3)
Nach einer Laminierzeit von 1 Stunde	vollständig	teilweise	vollständig	vollständig
Nach einer Laminierzeit von 72 Stunden	vollständig	keine	vollständig	nicht bestimmt
Oberflächengüte: (visuell)	keine Einfallstellen glatte Oberfläche	sehr viele Einfallstellen	keine Einfallstellen glatte Oberfläche	keine Einfallstellen glatte Oberfläche
Klebfreizeit bei 20 °C	35 Minuten	ca. 1 Stunde	2,5 Stunden	ca. 1,5 Stunden
Bruchdehnung	> 6 %	> 6 %	4,5 %	1,5 %
Glasübergangstemperatur: (Testmethode 2)	50 °C	nicht bestimmt	40 °C	70 °C

The result:

The gelcoat formulation according to the invention has significantly better adhesion properties than the non-invention gelcoat formulation, even after 72 hours of lamination time and then 5 hours of curing of the composite in the vacuum bag at 80 °C. The surface of the gelcoat layer according to the invention does not show any interference from impacting and thus differs from non-invention gelcoats PUR. Compared to the commercial EP coats, the gelcoat according to the invention has a significantly shorter free-flow time. In addition, the gelcoat formulation according to the invention shows a much higher fracture strength and width of adhesion than the gelcoat layer according to the invention. The T-Coat formulation is also significantly more flexible than the EP coat at 40 °C. This is also significantly higher than the T-Coat formulation at 70 °C. The T-Coat formulation is also significantly more flexible than the EP coat at 70 °C. This is also significantly higher than the T-Coat formulation at 70 °C.

Claims (20)

1. Use of a two-component composition that comprises

   A) a polyol component that comprises one or more polyols and one or more aromatic amines and possesses a hydroxyl group concentration of 0.5 to 10 mol hydroxyl groups per kg of polyol component, and

   B) a polyisocyanate component that comprises one or more aromatic polyisocyanates, for manufacturing polyurethane gel coats for synthetic resin composites, wherein the synthetic resin contains epoxy resin and/or vinyl ester resin and is not or not completely cured when brought into contact with the gel coat, and wherein the polyol component comprises

   A1) one or more low molecular weight polyols with a molecular weight of 150 to 6000 g/mol and a hydroxyl group concentration of 4 to 20 mol hydroxyl groups per kg of low molecular weight polyol and/or

   A2) one or more higher molecular weight polyols and

   A3) one or more aromatic amines.
2. Use according to claim 1, characterised in that the elongation at break of the gel coat at 23 °C is at least 3 %, preferably greater than 4 %, especially greater than 5 % (measured according to DIN EN ISO 527).
3. Use according to claim 1 or claim 2, characterised in that the polyurethane gel coat is not completely cured when brought into contact with the synthetic resin, wherein the bringing into contact with the synthetic resin is preferably made by depositing the synthetic resin onto the gel coat.
4. Use according to one of the previous claims, characterised in that the employed synthetic resin contains one or more reinforcing materials.
5. Use according to claim 4, characterised in that the reinforcing material is glass fibre fabric, glass fibre matting, carbon fibre fabric and/or carbon fibre bonded fabric, wherein the added synthetic resin is particularly preferably a prepeg or injection resin, in particular an injection resin or epoxy resin prepeg with glass fibre fabric and/or glass fibre matting.
6. Use according to one of the previous claims, characterised in that the polyol component contains one or more polyether polyols.
7. Use according to one of the previous claims, characterised in that the aromatic amine, dissolved in toluene (20 wt % amine in toluene), when mixed with an equimolar quantity of an oligomeric HDI isocyanate with an NCO content of about 5.2 mol/kg and a viscosity in the range of 2750 to 4250 mPas, mixed in toluene (80 wt % isocyanate in toluene), affords a gel time of more than 30 seconds, preferably more than 3 minutes, more preferably more than 5 minutes, in particular more than 20 minutes (measured according to E-DIN VDE 0291-2, 1997-06, point 9.2.1).
8. Use according to one of the previous claims, characterised in that the aromatic amine is a methylenebisaniline, in particular a 4,4'-methylenebis(2,6-dialkylaniline).
9. Use according to claim 8, characterised in that the aromatic amine is 4,4'-methylenebis(3-chloro-2,6-diethylaniline).
10. Use according to one of the previous claims, characterised in that the content of aromatic amine in the polyol component, based on the total amount of the polyol and aromatic amine, lies in the range from 0.1 to 20 wt %, preferably 0.3 to 10 wt %, more preferably 0.5 to 5 wt %, and in particular 1 to 3 wt %.
11. Use according to claim 1, characterised in that the content of low molecular weight polyol in the polyol component, based on the total amount of polyol and aromatic amine, lies in the range from 2 to 70 wt %.
12. Use according to claim 11, characterised in that the content of low molecular weight polyol in the polyol component, based on the total amount of the polyol and aromatic amine, lies in the range from 5 to 60 wt %, preferably 10 to 50 wt %, more preferably 20 to 45 wt. %, and in particular 35 to 45 wt %.
13. Use according to claim 1, characterised in that the hydroxyl group concentration of the low molecular weight polyols lies in the range of 5 to 12 and in particular in the range of 6 to 10 mol hydroxyl groups per kg of low molecular weight polyol.
14. Use according to claim 1, characterised in that the low molecular weight polyol is selected from straight chain or branched polyester polyols, polyether polyols, such as polyether glycols, acrylate polyols and polyols based on dimeric fatty acids.
15. Use according to claim 1, characterised in that the higher molecular weight polyol is selected from polyester polyols and polyether polyols, acrylate polyols and polyols based on dimeric fatty acids.
16. Use according to claim 1, characterised in that the content of higher molecular weight polyol in the polyol component, based on the total amount of the polyol and aromatic amine, lies in the range 75 to 10 wt %, preferably 65 to 10 wt %, more preferably 50 to 12 wt. %, and in particular 30 to 15 wt %.
17. Use according to one of the previous claims, characterised in that the aromatic polyisocyanate is monomeric, oligomeric or polymeric polyisocyanate.
18. A process for manufacturing synthetic resin composites with gel coats, said process including

    (i) mixing a two-component composition that comprises

    A) a polyol component that comprises one or more polyols and one or more aromatic amines and possesses a hydroxyl group concentration of 0.5 to 10 mol hydroxyl groups per kg of polyol component, and

    B) a polyisocyanate component that comprises one or more aromatic polyisocyanates,

    and at least partial curing of the mixture and

    (ii) bringing the mixture into contact with synthetic resin, wherein the synthetic resin contains epoxy resin and/or vinyl ester resin and is not or not completely cured when brought into contact with the gel coat and wherein the polyol component comprises

    A1) one or more low molecular weight polyols with a molecular weight of 150 to 6000 g/mol and a hydroxyl group concentration of 4 to 20 mol hydroxyl groups per kg of low molecular weight polyol and/or

    A2) one or more higher molecular weight polyols and

    A3) one or more aromatic amines.
19. A synthetic resin composite with polyurethane gel coat, manufacturable according to the process of claim 18.
20. The composite according to claim 19, characterised in that it is a wind turbine blade or a part thereof.